The invention resides in a method of manufacturing mold inserts by the galvanically depositing a metal in cavities formed in an electrically insulating material disposed on an electrically conductive substrate and then removing the metal from the substrate and other structures.
Microstructures are manufactured in large numbers and at low costs mold thermoplastic materials in molding processes such as injection molding and hot deformation. The forming elements in such molding processes are mold inserts which are brought into contact with the plastic at raised temperatures. The relief of the microstructures formed by such a molding procedure is therefore determined essentially by the three-dimensional shape of the surface of the form insert.
In the publication "Molding of Three Dimensional Microstructures by the LIGA Process" in the Proceedings of the Conference MEMS '92, which was held in 1992 in Travenmunde, Germany, the authors, M. Harmening et al., describe on pages 202 to 207 a method for manufacturing mold inserts with several structure planes. In this process, first, a mold insert is made by X-ray depth lithography and galvanic deposition of nickel which mold insert is then used to produce a single plane microstructure of PMMA by molding. This single plane microstructure of PMMA is then structured by X-ray depth lithography in such a way that another structure plane is generated. From this microstructure, a mold insert with two structure planes is formed by another galvanic nickel deposition. With repeated application of this process mold inserts of complex shapes and very small structural dimensions can be made. The process however has the disadvantage that several irradiation procedures at a synchrotron site are required during manufacture. As a result, the manufacturing costs are relatively high.
In the publication "Microvalve System Fabricated by Thermoplastic Molding" by J. Fahrenberg et al., presented in the Workshop Digest of the Conference Micro-Mechanics Europe '94, which was held in 1994 in Pisa, there is described on pages 178-181 a microvalve system produced by molding utilizing a mold insert with four structure planes. This mold insert was made by precision mechanical working of a brass plate. However, with such a process, very small structures cannot be generated because the smallest available cutting heads have a diameter of about 300 .mu.m so that certain minimum dimensions are given.
It is the object of the present invention to provide a method of making mold inserts, which, on one hand, have complex three dimensional shapes and, on the other, have very small structures.